As is well known, antitumor antibiotic agents can be produced via the fermentation of a variety of microorganisms. Antibiotic tropolone compounds were discussed by Nozoe et al in "Synthesis of Puberulonic Acid", Bull. Chem. Soc. Japan, 33 (1960) pp. 1071-4.
In 1981 and 1983, researchers reported on the action of colchicine and analogs thereof in treating P388 leukemia in mice. See Quinn et al, "Quantitative Structure--Activity Relationships of Colchicines against P388 Leukemia in Mice", J. Med. Chem., 24 (1981) pp. 251-6 and Brossi et al, "Biological Effects of Modified Colchicines . . . ", J. Med. Chem., 26 (1983) pp. 1365-9.
U.S. Pat. No. 4,656,192 to Yamato discloses alkyl- and hydroxy-substituted tropolones and their use as anti-tumor agents.
Synthesis and antitumor activity of compounds containing two tropolone moieties are described by Yamamoto et al., "Synthesis and antitumor activity of tropolone derivatives . . . ", J. Med. Chem., 35 (1992) pp. 267-273. A natural product containing two tropolone units has been isolated by Sasade et al , "Structure of Fusariocin C . . . . ", Agric. Biol. Chem., 45 (1981) pp. 1689-1692.